Can you guess what these are pictures of?

Butterfly proboscis

Hair (from a hare)

Pollen grains

Salt grains

Snowflakes

Fly’s Eye

Lesson 2 - Microscopy Learning Objectives: Compare and contrast light microscopes and electron microscopes. Explain how the invention of electron microscopes was impacted the study of cells. Carry out magnification calculations. Practical skills: Be able to prepare a slide and use a microscope.

Video: Microscopes https://www.brainpop.com/technology/scienceandindustry/microsco pes/ Watch the video and answer the following questions. What are the different types of microscopes? Give a BRIEF description of how they work.

Microscopes The images from the starter were taken using an electron microscope. Electron microscopes use a beam of electrons to capture an image. Electron microscopes can magnify images up to 10,000,000 X. Light microscopes are simpler and use lenses to focus visible light and magnify an image. Light microscopes can magnify images up to 2,000 X.

Light Microscope Lenses – magnification Eyepiece lens Lenses – magnification Focusing wheels – moves the stage up and down to focus the image Stage – holds the slide Slide – transparent glass to hold the specimen Light source – to provide light to form a magnified image Fine focusing wheel Objective lens Slide Coarse focusing wheel Light source Stage

Practical: Observe onion and cheek cells You will now prepare a slide of onion skin tissue and cheek cells to observe through the microscope. Watch the demo of how to prepare a slide. Follow the instructions carefully and make detailed drawings of the cells you observe. Required practical skills: Use a light microscope to observe, draw and label a selection of plant and animal cells. A scale magnification must be included.

Demo: Preparing an Onion Skin Slide https://www.youtube.com/watch?v=eD1CdfRycqs

Different Microscopes have different Magnification and Resolution Magnification = increasing the size of an image, how many times bigger an image is from the actual object (ie 2500X) Resolution = the level of detail that can be observed, the smallest unit that can be distinguished as separate (ie 1 nm) Magnification = 𝑠𝑖𝑧𝑒 𝑜𝑓 𝑖𝑚𝑎𝑔𝑒 𝑠𝑖𝑧𝑒 𝑜𝑓 𝑜𝑏𝑗𝑒𝑐𝑡 Magnification = magnification of eyepiece lens x magnification of objective lens (light microscope)

Electron Microscopes Electron microscopes have higher magnification and better resolution. This means that it can be used to study cells in more detail. This has enabled biologists to see and understand many more sub- cellular structures (like mitochondria).